The present invention relates to a chuck for gripping workpieces and more particularly to a chuck suitable for gripping pieces having a shaft and an enlarged offset, such as a hub or flange, proximate the end of the shaft that is gripped by the chuck.
Draw down chucks are widely used to grip workpieces while machining or performing other operations. Chucks come in a variety of sizes to grip various sized workpieces. Typically, chucks have two to four jaws that move axially between an extended position and a retracted position. As the jaws retract, they axially move together to grip the outer or inner surface of a workpiece. Chucks that close and open only through axial movements of the jaws rods have difficulty in retaining or gripping workpieces with larger diameter hubs or flanges. Even if the chuck is designed to accept a workpiece having large diameter portions, the jaw rods need an extended length of travel to open wide enough to accept such a workpiece. Extended travel causes the jaw rods to have large unsupported areas that are susceptible to distortion or warping. For chucks that grip the inner diameter of a workpiece, extended travel is often not possible due to the configuration of the workpiece.